Gallium arsenide single‐crystal layers, doped with119Sn‐enriched tin, have been prepared by liquid‐phase epitaxy and characterized by119Sn Mo¨ssbauer spectroscopy (MS) and Hall measurements. Two Sn sites are observed by MS, and the population of one of these (site A) matches the carrier concentration in as‐grown material, therefore allowing the MS parameters of this site to be positively identified as those of the SnGadonor in GaAs, and thereby showing no evidence for compensation. The population of the second type of Sn (site B) increases with the total Sn concentration, and this site is clearly electrically inactive. The site B MS parameters are similar to those of Sn3As2, SnAs, and &bgr;‐Sn, thereby demonstrating that microprecipitates of these phases may often exist in heavily Sn‐doped liquid‐phase‐epitaxial GaAs. Site B could also be due to clusters of Sn and/or Sn‐As that are precursors to the formation of distinct precipitates of Sn3As, SnAs, or &bgr;‐Sn. Annealing experiments yield a Sn‐related acceptor that is very likely of the form SnGaVGa. In addition, precise MS parameters are reported for the intermetallic phases SnAs and Sn3As2.